An array of techniques, from SPECT scans (in concert with science core SPECT project), to computer based video tasks, to social skills tasks, will be employed to determine the parameters of competence which undergird the emergence and development of representational function and symbolic communicative processes in human and nonhuman primates. Using recently developed sophisticated interactive computer programs which permit apes to interact with video images in a variety of formats, we will assess their ability to comprehend and produce complex grammatical structures. Systematic human-ape comparisons of word acquisition will investigate whether or not both apes and children respond to linguistic input by employing similar methods of inference to break the semantic code. We will investigate not only the specifics of word learning, but the means by which more general cognitive interpretations of the context arise, and the manner in which such interpretations permit inferences about the state of knowledge of communicative partners. Tests will be devised to assess the degree to which such knowledge is present and operable in normal children of various ages, in apes and in autistic children. In addition, we will attempt to expand the communicative abilities of apes into the vocal domain, with the longterm intent of developing techniques to foster vocal communication in children with retardation. Finally, tests of semantic and grammatical competency will be developed for use with SPECT imaging techniques (see scientific core) which will permit us to determine the neurological substrates of these skills and to assess the degree to which the substrates of linguistic capacity differ between ape and man.